The broad long-term purpose of Core C is to provide the individual projects with access to synthesis of peptides, the synthesis of peptide libraries, and high throughput assays.. The specific aims of the core are 1) to produce individual peptides and peptide libraries for use in examining the interaction of various nuclear receptors with representative NR box sequences; 2) to produce recombinant nuclear receptors (particularly TR and ER) for use in screening assays; 3) to assay the binding of ligands and peptides to nuclear receptors, both in high throughput initial assays and in more precise biophysical characterization of particular interactions; 4) To facilitate and increase efficiency for other assays used in the individual projects by adapting them to the microtiter plate format. The research methods of the core will include the solid phase synthesis of peptides, the parallel synthesis of peptide libraries, the combinatorial synthesis of peptide libraries, the assay of protein peptide binding by fluorescence polarization, the assay of transcriptional activation by luminescence, and other assays by fluorescence intensity and absorbance intensity.